INTERSTATE LEAKING GRAY WATER, PART 3: TANK RE-INSTALL

In Part 1 of this series, I described the leaking gray water tank problem exhibited by our 2007 Airstream Interstate.  In Part 2, I described how we removed our tank and rehabbed some of the ancillary fittings.

In this post, I describe how we retrofitted and re-installed the tank, but please keep one important caveat in mind:  We have no way of knowing whether this chosen solution will prove up in actual motorhome use.  Airstream has not released any technical guidance on how to resolve this issue (so they told my husband by telephone).  Therefore, we had nothing to go by except our empirical wisdom as DIYers and our rudimentary understanding of why this problem originated in the first place.

We suspect it occurred because the gray water system as designed did not incorporate any means of shock absorption (bumps and vibrations deriving from normal road driving) and also because the gray water tank was not adequately braced in its cradle (lateral bracing was good but we found a lot of "play" longitudinally, with the tank able to move back and forth a few inches once unhooked from its pipes).  Given the applied stresses, the joinery appears to have simply failed at its weakest point, which proved to be the tank junction.  This is a photo of the original galley sink drain line where it should have been connected to the tank.  

If we later discover this procedure to be insufficient in resolving this problem, we will revert and modify this post accordingly.  In the mean time, here is an account of our reconfig.

You've no doubt heard the expression "bend, don't break"?  This flexible rubber fitting (specs given below) was part of what we used to modify the tank connection ports.   

I said bend, don't break.  Very important here.  

In order to make this rubber inlet gasket fit, we had to first prepare the holes where the previous pipes had sheared off.

In this pic above, my husband is using a dremel tool to carve a channel through the remaining fragment of threaded ABS pipe.  

Once it is cut through, that piece can be popped out.  

He proceeded with the dremel tool until he had notched all the way through the polyethylene connector.  

Then he used a sharp blade to whittle that down to the level of the tank top.  Once that occurs, this piece, too, can be largely pried out of the hole.  

Here's the partially-finished hole with a clearer view of the gasket part numbers.  

How do you know when your holes are sufficiently cleaned up?  The gasket fits smoothly in them.  The depth of the channel is the same as the outer diameter (O.D.) of the inlet itself.  

This is what a sufficiently-cleaned hole looks like.  Perfection is not required.  

This is the sealant that we used to attach the new inlet fittings to the tank.  It's not exactly what the fitting manufacturer recommended, but it was the closest product that my husband could find in common hardware stores.  

You better have a good supply of disposable gloves, because this is messy and this product sets up fast.  

It takes a bit of force to get it into the hole such that the channel is seated properly around the hole edges.  And then once it's in, you should briefly insert a scrap end of the correct diameter pipe to make sure that the rubber is pushed out into sufficient roundness.  

My husband added more cement to the outside of the connection.  He used an old teaspoon to smooth it.  Spread out this way, it looks very much like the material that had originally been used on the tank.  

We also replaced the reducer on the part that leads to the dump valve.  

Same neoprene sealant.  

Do not ask me why this hose clamp had originally been added to bind these two essentially-uncompressible parts. We replaced it anyway.  

The sequence above seems like a major hassle, but my husband was able to clean up each hole and fit all those new parts in about an hour's time (versus several hundred dollars to buy a new tank that we were afraid might not constitute an improvement over this one).  As with any DIY, the key is having the correct tools on hand.  If you don't have an appropriate supply of tools, you will probably struggle with a job like this.

A few days after we got these new modified inlet ports installed, a thread titled "The Flood" appeared on Air Forums Sprinter and B Van Forum.  That thread described a sink faucet design flaw that can quickly result in Airstream Interstates being flooded on the interior as a result of gray water tank overflow.  Seeing this, we diverted our attention to the addition of an emergency relief valve on the tank itself.  As the forum thread revealed, the defect can also be addressed by taking a hacksaw to the faucet handle in order to shorten it, and that may be an easier workaround for many owners.  However, because our tank was already de-installed from our vehicle at the time the thread appeared, it was not a lot of extra work to install an overflow (which we would have eventually done anyway because we don't trust the fill sensors), and you can read about that in this post.

Now, onto the re-install.

Once the rubber tank inlets are fitted on the tank, this becomes a fairly simple matter of reconnecting the original lines to the tank.  This part is sort of like "regular plumbing" except that we inserted rubber couplings into the lines because, again, this assemblage needs to bend, not break as it did following the original installation by Airstream.

I will post a series of pics below to demonstrate the general approach and materials, but I won't overload this post with step-by-step details because your own configuration may be a bit different and also because there is more than one way to string pipe successfully.  If you have specific questions regarding your own situation, please feel free to contact us via interstate.blog - at - gmail.

One of our biggest challenges was that the system uses ABS piping which is almost impossible to buy in our part of the country because it isn't used here any longer (local plumbing codes dictate what materials are available in any given geographic region, which is another reason why I am not overloading this post with step-by-step detail).  We only managed to scare up a single piece of the pipe itself from a local supplier called Dues Camping Center.  The rest we just cobbled together from scraps of the original pipe.  

Removing one of the old P-traps:  You will use a Saws-All or other powered equipment right next to the diesel tank NOT!  Here you can see my husband using a manual cable saw (red handles) to safely cut out this old section of plumbing, and that solid grey mass you see at photo bottom is the fuel tank for the vehicle.  There is almost no clearance between the two structures.  Remember to be safe if you're messing with this stuff (see BIG FAT DISCLAIMER).

Here I was holding onto the P-trap so that the cable saw would not get bound up and so that, once the pipe was cut through, it would not come tumbling down upon us, dumping its nasty water on our heads.  You can see a drip of water on the bottom of it... it had a slow leak for reasons that were not clear, and so we replaced it.

My husband stresses that no power tools were used in this area beneath the vehicle for safety reasons.  He also used a really large diameter manual pipe cutter where necessary.  

A flexible coupling spliced into the line leading from the galley sink to the grey water tank.  Flexible couplings provide several advantages in an application such as this:
(1) They bend forgivingly.
(2) The ABS segments can be re-positioned within the coupling ends as needed to adjust the pipe fit, rather than making the entire assemblage hard-piped which requires a lot of precision of the type that is difficult to achieve in a DIY situation, especially where materials are limited (ABS pipe not being available here).
(3) The lines can be disassembled later if necessary without having to break any hard connections.

BTW, that thin white wire you see zip-tied to the red PEX water line is part of the sensor wire that extends from our coach battery (which is located under the passenger seat) to the new charger / converter (which is located roughly amidships).  You can read about that upgrade in this post.  

One view of the reconfig'd assembly leading to the grey water tank. You can see yet another flexible coupling in this assemblage (right side of photo).  Note also that there is a hose clamp around the rubber inlet fitting that was installed on the tank.  That, too, can be later removed if it proves necessary to perform additional work in or around this tank.  

Very important - make sure you use a spray foam sealant to plug any gaps that are created during this re-plumbing.  Not only will this stop drafts, it will also help to discourage rodents which will seize any opportunity to enter your coach.  

Here is a view of the re-installed "heat shield" showing three new segments of stainless steel all-thread with washers and nuts on the bottoms (the originals were so rusty that we decided to upgrade).  This is looking toward the front of the vehicle at the zig-zag-shaped tank shield with the diesel tank in front of it).   

Rather than closing this post with an internet meme as I usually do, I will instead relate a moment of comic relief that we experienced during this project.

At one point, my husband had placed the gray water tank in the driveway of our home in preparation for loading it into his car.  Our teenage daughter spotted this and, not knowing what it was, she asked, "What's with the Picasso in the front yard?  Is that going to become another of your lawn sculptures?"  (We are just as much into DIY around the house as we are with the Interstate, so she is accustomed to my unconventional projects and design choices).  And I said, "Huh?  What are you talking about?  What Picasso?!?!"  And then I realized that she was right - there is a certain artistic conformance.

Echoing the great master Pablo in a neo-Cubist conspiracy, or just a coincidence?
:-)
The top photo is a sculpture on display this past summer in the Museum of Modern Art (MOMA).  We went to MOMA in a minivan, all the way from Houston Texas.  Next summer I'm hoping that we will make a similar trip in this Airstream Interstate, if we can only get all its necessary repairs and upgrades completed.